1. Field of the Invention
The present invention pertains generally to eye tracking technologies, and more particularly to precision eye tracking through use of relative iris edge based landmarks in eye geometry.
2. Background Information
In addition to the eyes being the “gateway to the soul” (Herman Melville), a subject's eyes are an incredibly sensitive bio-indicator that can be utilized for many functions.
Eye movement is the voluntary or involuntary movement of the eyes, helping in acquiring, fixating and tracking visual stimuli. In addition, rapid eye movement (REM) occurs during REM sleep.
“Eye tracking is the process of measuring either the point of gaze (“where we are looking”) or the motion of an eye relative to the head. An eye tracker is a device for measuring eye positions and eye movements. Eye trackers are used in a wide array of applications including research in numerous fields, medical diagnosis, psychology, in cognitive linguistics and even in advertising and product design. There are a number of methods for measuring eye movements. The most popular variant is a non-invasive technique that uses video images from which the eye position is extracted. Other methods use search coils or are based on the electro-oculogram. The non-invasive technique for recording eye position relative to the head using a camera to record eye position relative to the head is also known as video oculography or VOG. VOG systems are used by Vestibular Researchers, Ophthalmologist, Otolaryngologists, Physical Therapists, Neurologists, Audiologists, Balance Clinicians, Neurophysiologists, Physiologists, Neuroscientists, Occupational Therapists, and others.
The most widely used current designs are video-based eye trackers. A camera focuses on one or both eyes and records their movement as the subject viewer will often look at some kind of stimulus. Most modern eye-trackers use contrast to locate the center of the pupil. Image processing software is utilized to interpret the images to provide objective data of eye position. This type of image processing software is described in “A GEOMETRIC BASIS FOR MEASUREMENT OF THREE-DIMENSIONAL EYE POSITION USING IMAGE PROCESSING” Vision Res. Volume 36. No. 3, Moore et al., pp 445-459, 1996, which is incorporated herein by reference. In general, most eye tracking devices digitize an image of the, define the pupil using the high contrast difference between the pupil and the rest of the eye, and then define the center of the pupil by approximating a circle of the same size or calculating the centroid of the pupil itself. For relatively large-scale eye movements, such as saccades and nystagmus, this method is appropriate despite of the fact that the pupil changes in size and, to a lesser degree, shape.
Accurate eye position recording and monitoring in three dimensions (3D-yaw, pitch and torsion rotation about line of sight) is a significant clinical diagnostic tool in the field of vestibular disorders such as vertigo and other neurological disorders.
There is a need for greater precision in eye tracking systems.